Comparative dynamics study of role interchange of shaft and bearing in a planar four-bar mechanism with clearance

This study investigates the impact of interchanging the shaft-bearing roles between the crank and the connecting rod on the dynamics of a planar four-bar mechanism containing a revolute joint with clearance. Two configurations are compared with identical geometry, material and clearance: (i) crank as shaft and (ii) crank as bearing. First, the study establishes a theoretical framework that details how both cases behave differently. Afterward, high-fidelity simulations in MSC Adams are used to quantify mean/RMS/peak accelerations, normal contact forces, flight time, and contact area probability over 100 to 2000 RPM. The results indicate a significant dependence on the configuration. Case 1 exhibits higher peaks and longer flight intervals, while case 2 produces more localised contact and concentrated wear. An experimental setup was used to validate acceleration trends at 100 and 130 RPM. The findings of this study have significant implications for applications that require high accuracy and provide useful information on vibration analysis for clearance joints mechanisms. Although fundamental mechanical design norms establish baseline joint configurations, this study provides a complementary quantitative framework demonstrating how the assignment of the motion-applying versus motion-receiving body alters penetration depth, contact pressure, dynamic response and wear progression.